Illumination optical system and exposure apparatus

ABSTRACT

An illumination optical system that is used for an exposure apparatus that includes a mirror and exposes an object, illuminates a surface to be illuminated using light from a light source, and includes a filter member arranged at a position that substantially has a Fourier transform relationship with the surface to be illuminated, the filter member including a transmittance distribution preset to correct a non-uniformity of a transmittance distribution of the illumination optical system caused by the mirror.

This application is a continuation of prior application Ser. No.11/144,710, filed Jun. 2, 2005, now U.S. Pat. No. 7,345,741 to whichpriority under 35 U.S.C. §120 is claimed. This application also claims abenefit of priority based on Japanese Patent Application Nos.2004-166552, filed on Jun. 4, 2004, and 2005-116585, filed on Apr. 14,2005, both of which are hereby incorporated by reference herein in theirentirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates to an illumination optical system, andmore particularly to control over an incident angle distribution orlight distribution characteristic (also referred to as “effective lightsource” and “a distribution”) on a surface to be illuminated (“targetsurface”). The inventive illumination optical system is suitable for anexposure apparatus for the micro-lithography used to manufacture finepatterns such as semiconductor devices, liquid crystal devices (“LCDs”)and magnetic materials.

A projection exposure apparatus has been conventionally employed whichuses a projection optical system to project a circuit pattern of areticle (or a mask) onto a wafer, etc. to transfer the circuit pattern,in manufacturing such fine semiconductor devices as a semiconductormemory and a logic circuit using the photolithography technology. Alongwith the recent demands for smaller and lower profile electronicapparatuses, the finer processing to the semiconductor devices mountedon the electronic apparatuses are increasingly required. One known meansfor achieving the high resolution is to increase the numerical aperture(“NA”) of the projection optical system (high NA scheme).

In addition, for the high-quality exposure, an effective light sourceshould be optimized in accordance with a pattern of the surface to beilluminated, such as a reticle. For example, the effective light sourcedistribution is implemented by adjusting an intensity distribution neara fly-eye lens's exit surface to a desired shape, such as a normalillumination condition, an annular illumination condition and aquadrupole illumination condition. A projection exposure apparatus isrequired to have a means for optimizing the NA of the projection opticalsystem, a coherence factor σ that is the illumination optical system'sNA/the projection optical system's NA and the effective light source toprocesses having various characteristics.

The optical path in the recent illumination optical system becomeslonger as the required function diversifies, e.g. a function of formingvarious effective light sources. It is therefore difficult to arrangethe illumination optical system along a straight line, and it isnecessary to deflect the optical path using a deflection mirror so as toreduce the size of the exposure apparatus. One known means formonitoring the exposure dose is to provide the illumination opticalsystem with the half-mirror and to monitor the transmitting lightthrough or reflected light from the half-mirror.

When the incident exposure light spreads in the deflection mirror or thehalf-mirror, the incident angle of the light can differ according tolocations in the mirror. The conventional design technology hasmaintained mirror's transmittance or reflectance fluctuations within thelatitude, but recently had difficulties in doing so as the high NAscheme advances in accordance with the fine-processing request. Inaddition, a usable coating material is limited for use with the mirrorand the light having a wavelength of 250 nm or smaller, and the designfreedom is limited accordingly.

Therefore, a desired effective light source distribution could beobtained when no mirror is used, but when the mirror is used, itstransmittance and reflectance characteristics preclude a formation ofthe desired effective light source distribution. This problem causes apattern to be exposed with a coherence factor σ different from theoptimized one that provides a transfer of the minimum critical dimension(“CD”) of the pattern, thereby preventing the designed resolution CD (inparticular minimum CD) from being obtained. In addition, another problemof “HV difference” occurs which is a difference between horizontal andvertical CDs transferred on a wafer, lowering the yield.

Moreover, the contrast of the interference fringe of a line and space(“L & S”) pattern formed on the photosensitive agent lowers when thediffracted light from the L & S pattern is the p-polarized light. Thisdecrease becomes striking as the high NA scheme proceeds. Accordingly,studied as a solution for this problem is a polarized illumination thatutilizes the s-polarized light, in which a vibration direction of anelectric field vector of the light is parallel to the wafer surface andperpendicular to the light traveling direction. Nevertheless, thes-polarized light and the p-polarized light have differenttransmittances and reflectances on the mirror and cause a similar HVdifference.

Prior art for solving the non-uniformity of the transmittancedistribution in the illumination optical system includes, for example,Japanese Patent Applications, Publication Nos. 2002-093700, 2003-243276,and 2002-75843.

While Japanese Patent Application, Publication No. 2002-093700 proposesa correction of the transmittance by adjusting an angle between twofilters each having a discrete transmittance distribution, the angularadjustment requires a measurement of the actual effective light sourceand a long time. Another problem is that the discrete transmittancedistribution cannot improve the correction accuracy. On the other hand,Japanese Patent Application, Publication No. 2003-243276 has a purposeto correct the non-uniformity of the transmittance caused by an incidentposition upon the lens, but does not consider the non-uniformities ofthe reflectance and transmittance caused by an incident angle upon amirror.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to an illumination optical system thatobtains a desired effective light source relatively easily and quickly.

An illumination optical system according to one aspect of the presentinvention that illuminates a surface to be illuminated using light froma light source, and includes a light shaping member for transforming thelight from the light source and for forming a predetermined light shapeon a surface that has a Fourier transform relationship with the surfaceto be illuminated, an effective light source forming member for formingan effective light source using a light from the light shaping member asan incident light, a plurality of light shielding members that arearranged near the surface and that shield a part of the lighttransformed by the light shaping member and that are movableindependently from each other, wherein the plurality of the lightshielding members move based on the change of a shape of the effectivelight source.

An illumination optical system according to another aspect of thepresent invention that illuminates a surface to be illuminated usinglight from a light source, and includes a light shaping member fortransforming the light from the light source and for forming apredetermined light shape on a surface that has a Fourier transformrelationship with the surface to be illuminated, an effective lightsource forming member for forming an effective light source using alight from the light shaping member as an incident light, a plurality oflight shielding members that are arranged near the surface and thatshield a part of the light transformed by the light shaping member andthat are movable independently from each other, and a polarizationsetting member for setting a polarization of the effective light source,wherein the plurality of the light shielding members move based on thechange of at least one of a shape of the effective light source and thepolarization of the effective light source.

An illumination optical system according to another aspect of thepresent invention that illuminates a surface to be illuminated usinglight from a light source, and includes a light shaping member fortransforming the light from the light source and for forming apredetermined light shape on a surface that has a Fourier transformrelationship with the surface to be illuminated, an effective lightsource forming member for forming an effective light source using alight from the light shaping member as an incident light, a plurality oflight shielding members that are arranged near the surface and thatshield a part of the light from the light source, wherein each of theplurality of the light shielding members is insertable into andejectable from the optical path at each of a plurality of positions inan optical axis direction of the illumination optical system.

An illumination optical system according to another aspect of thepresent invention that illuminates a surface to be illuminated usinglight from a light source, and includes a light shaping member fortransforming the light from the light source and for forming apredetermined light shape on a surface that has a Fourier transformrelationship with the surface to be illuminated, an effective lightsource forming member for forming an effective light source using alight from the light shaping member as an incident light, a first lightshielding member that shields a part of the light from the light sourceand that is insertable into and ejectable from the optical path near thesurface, and a second light shielding member that are arranged near thesurface and that shield a part of the light from the light source, thesecond light shielding member including a plurality of light shieldingportions that are movable independently from each other.

An illumination optical system according to another aspect of thepresent invention that illuminates a surface to be illuminated usinglight from a light source, and includes a light shaping member fortransforming the light from the light source and for forming apredetermined light shape on a surface that has a Fourier transformrelationship with the surface to be illuminated, an effective lightsource forming member for forming an effective light source using alight from the light shaping member as an incident light, a plurality oflight shielding members that are arranged near the surface and thatshield a part of the light from the light source, wherein each of theplurality of the light shielding members includes a plurality of lightshielding portions that are movable independently from each other.

Other objects and further features of the present invention will becomereadily apparent from the following description of the embodiments withreference to accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structure of an exposure apparatus according toone aspect of the present invention.

FIG. 2 is a schematic structure of a light shaping means in the exposureapparatus shown in FIG. 1.

FIGS. 3A to 3C are schematic plane views for explaining an operation ofa light adjusting means in the exposure apparatus shown in FIG. 1.

FIGS. 4A to 4C are schematic plane views for explaining anotheroperation of the light adjusting means shown in FIG. 1.

FIGS. 5A to 5C are schematic plane views for explaining still anotheroperation of the light adjusting means shown in FIG. 1.

FIG. 6 is a graph for explaining a non-uniformity of a transmittancedistribution caused by mirrors in the exposure apparatus shown in FIG.1.

FIG. 7 is a schematic plane view for explaining a non-uniformity of atransmittance distribution caused by the mirrors in the exposureapparatus shown in FIG. 1.

FIGS. 8A to 8C are schematic plane views of filter members in theexposure apparatus shown in FIG. 1.

FIG. 9 is a flowchart of one illustrative illumination method for theexposure apparatus shown in FIG. 1.

FIGS. 10A to 10C are schematic view for explaining operations ofdifferent types of σ shape correction mechanisms in the exposureapparatus shown in FIG. 1.

FIGS. 11A to 11C are schematic plane views of the σ shape correctionmechanisms shown in FIGS. 10A to 10C.

FIG. 12 is a flowchart for explaining a fabrication of devices(semiconductor chips such as ICs, LSIs, and the like, LCDs, CCDs, etc.).

FIG. 13 is a detailed flowchart of a wafer process in step 4 shown inFIG. 12.

FIGS. 14A to 14E are views showing illustrative polarizations in thelight in the effective light source distribution.

FIG. 15 is a graph for explaining a non-uniformity of a transmittancedistribution of a polarization caused by the mirror in the exposureapparatus shown in FIG. 1.

FIGS. 16A and 16B are views of a phase plate structure, and an effectivelight source correction using a filter member and a stop in a polarizedillumination that generates different polarizations on a pupil.

FIG. 17 is an enlarged structure of an illumination optical system shownin FIG. 1 for a polarized illumination and for a non-polarizedillumination.

FIGS. 18A to 18C are views for explaining a method for setting atransmittance distribution to the filter in a tangentially polarizedillumination.

FIGS. 19A and 19B are views for explaining a method for setting atransmittance distribution to the filter in a cross-pole polarizedillumination.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will now be given of an exposure apparatus 1 according toone aspect of the present invention, with reference to the accompanyingdrawings. Here, FIG. 1 is a schematic structure of the exposureapparatus 1. The exposure apparatus 1 includes, as shown in FIG. 1, anillumination apparatus 100, a reticle 200, a projection optical system300, a plate 400, a plate stage 450, and a controller 500. The exposureapparatus 100 is a projection exposure apparatus that exposes a circuitpattern of the reticle 200 onto the plate 400 in a step-and-scan manner.However, the present invention is applicable to a step-and-scan exposureapparatus.

The illumination apparatus illuminates the reticle 200 that has acircuit pattern to be transferred, and includes a light source section102 and an illumination optical system 110.

The light source section 102 may use as a light source, for example, anArF excimer laser with a wavelength of about 193 nm, a KrF excimer laserof a wavelength of about 248 nm, etc. However, the type of the lightsource is not limited to the excimer laser and may use an F₂ laserhaving a wavelength of about 157 nm. The number of light sources is notalso limited. The light source section 102 when using a laser usespreferably an incoherently turning optical system that turns a coherentlaser beam into an incoherent one. A light source applicable to thelight source section 102 is not limited to the laser, but may use one ormore lamps such as a mercury lamp, xenon lamp, etc. The exposureapparatus 1 of this embodiment is effective to the light having awavelength of 250 nm, as described later.

The illumination optical system 110 illuminates the reticle 200, andincludes a lens, a mirror, an optical integrator, a stop, etc. Theillumination optical system 110 of this embodiment includes a lightshaping means 120, a light adjusting means 130, an imaging opticalsystem 140, plural deflection mirrors 112, 150 and 151, a filter member154, a fly-eye lens 156, a variable stop 158, a condenser optical system160, a half-mirror 152, a detector 170, a masking blade 172, and animaging optical system 180.

The deflection mirror 112 deflects the light from the light sourcesection 102 toward the light shaping means 120.

The light shaping means 120 shapes the light from the light sourcesection 102 into the light having a necessarily shaped distribution,such as a circle, an annular shape and a multi-pole shape, on apredetermined surface (surface A). In other words, the surface A is asurface that forms a base shape of the effective light source and adesired effective light source shape is made on the surface to beilluminated from the distribution having the base shape on the surfaceA, through shaping by the light adjusting means 130, which will bedescribed later, through sizing by the imaging optical system 140 havinga variable magnification, and through the limitation by stop members(such as the stop 158) arranged in place.

The light shaping means 120 includes an optical integrator as one of ora combination of a fly-eye lens, an optical pipe that reflects the lighton its internal surface, and a diffractive optical element (“DOE”), anda relay optical system, a condenser optical system, and a mirror, etc.The light shaping means 120 of this embodiment includes optical systems121, 123, 126, optical integrators 122 and 124, and DOEs 125 a and 125b. Here, FIG. 2 is a schematic structure of the light shaping means 120.

The optical system 121 is made of a cylindrical lens etc., and turns theincident light into a desired size, such as an approximate circle orsquare. The optical integrator 122 in this embodiment is a fly-eye lensthat has a two-dimensionally arranged micro-lenses (rod lenses) or itsequivalent, and uniformly illuminates an incident surface of the opticalintegrator 124 via the optical system 123. The light distribution shapeon the incident surface of the optical integrator 124 is determined bythe NAs of the micro-lenses in the optical integrator 122 and the focallength of the optical system 123, and is constant irrespective of thedistribution of the light incident upon the optical integrator 122.

The optical integrator 124 of this embodiment is a fly-eye lens that hasa two-dimensionally arranged micro-lenses (rod lenses) or itsequivalent, and uniformly illuminates the incident surface of the DOE125 a or 125 b. The light emitted from each area of the opticalintegrator 124 has approximately the same NA (or light divergent angle)throughout the areas.

The DOEs 125 a and 125 b are provided near the exit surface of theoptical integrator 124 and can be switched by a driver (not shown). Thenumber of DOEs is not limited two, and the driver is an apparatus, suchas a turret, for inserting one of the DOEs into the optical path. TheDOE is an element that diverges the incident light into a desiredangular distribution, and the angular distribution of the exit light isprojected onto the back focal surface (or so-called Fourier transformsurface) of the optical system 126. The surface A corresponds to thisFourier transform surface. The Fourier transform relationship is arelationship between an object surface and a pupil surface or arelationship between a pupil surface and an image surface.

In each of the optical integrators 122 and 124, an incident-side (orfront) focal point position approximately accords with the incidentsurface, and the angular characteristic of the light emitted from eachintegrator does not change even when the angle of the incident lightchanges. This configuration enables the light having a continuouslysteady, angular characteristic to enter the DOE, and the surface A has acontinuously steady light distribution even when the light from thelight source fluctuates. Each of the optical integrator 122 and 124 maybe an optical pipe that reflects the light on its internal surface, aDOE, a fly-eye mirror that serves as a multiple light sources formingmeans and includes plural reflective optical elements, plural opticalintegrator that combine them with each other, or another homogenizer.

The optical integrator 124 and the DOE spaced from each other so thatthe light from the adjacent micro-lenses in the optical integrator 124partially overlap each other. As the light that passes the opticalintegrator 122 and the optical system 123 illuminates the opticalintegrator 124, the DOE is uniformly irradiated without a concentrationof the light. For example, when the ArF laser is used as a light sourceand the DOE is made of quarts, the DOE gets damaged when the largeirradiation energy density concentrates on the part of the DOE. Thisarrangement serves as a preventive measure.

One reason why the optical integrator 124 is irradiated by the lightthat passes the optical integrator 122 and the optical system 123 is thesteady incident light distribution on the surface A. Even without theoptical integrator 122 or the optical system 123, a steady intensitydistribution is available on the surface A. However, as the lightdistribution incident upon the integrator 124 varies, the incident lightdistribution (or incident angular distribution) varies on the surface A.This means that the angular distribution of the incident light varies onthe reticle 200 surface to some extent. In other words, even when thereis a fluctuation and error of the incident light from the light source,this configuration provides the always steadily controlled lightdistribution and incident angular distribution on the surface A untilthe DOE is switched. The light shaping means 120 of this embodiment hasa double-integrator configuration but may use a triple-integratorconfiguration.

The pattern on the surface A is a convolution between a DOE Fourierpattern (which is a pattern formed on a Fourier transform surface whenthe light is perpendicularly incident at NA of 0) and the angulardistribution of the light incident upon the DOE. In order to make thedistribution on the surface A close to the desired distribution, it ispreferable to make the NA of the exit light from the optical integrator124 as small as possible. Therefore, it is desirable to preserve the NAx diameter of the light emitted from the optical system 121 if possibleand to transmit it to the DOE. By switching the DOE, a circular, annularor multi-pole distribution, for example, is formed on the surface A. Aproper design of the DOE can differently set the intensity of each polearea in the multiple poles, such as a quadrupole.

Turning back to FIG. 1, the light adjusting means 130 for furthertrimming a shape of the light that has been turned to the base shape bythe light shaping means 120 is provided switchably near the surface A.The light adjusting means 130 includes a conical optical element 132, aconical optical element 134 that can change an interval, aplane-parallel plate (not shown), a properly shaped stop member such asan annular aperture stop, a quadrupole aperture stop and a circularstop, a pyramid optical element and a tectiform optical element, and anenlarging/reducing beam expander for changing a magnification. The lightadjusting means 130 can retreat from the optical path, or can insertplural of the above components into the optical axis.

The conical optical element 132 has a conically concave, incidentsurface and a conically convex, exit surface and forms, for example, anannular light when it is arranged on the optical axis and the circularbase shape is formed on the surface A.

The conical optical element 134 includes an optical element 134 a havinga conically concave, incident surface and a plane exit surface, and anoptical element 134 b having a plane incident surface and a conicallyconvex exit surface. When the base shape on the surface A is a circleand the conical optical element 134 is arranged on the optical axis, theannular light is formed. By changing an interval between the opticalelements 134 a and 134 b, a shape (or a ratio of annulus) and the sizeof the annular light become variable. The thus configured conicaloptical element 134 can effectively form the annular light in a smallspace. Given a quadrupole or dipole base shape on the surface A, itsinternal diameter and outer diameter are made variable.

For example, given a proper selection of the DOE in FIG. 2 and anannular distribution (FIG. 3A) on the surface A, the shape of theannulus or a ratio of the annulus is variable by changing an intervalbetween the optical elements 134 a and 134 b, as shown in FIGS. 3B and3C. Given another DOE in FIG. 2 and an annular distribution (FIG. 4A) onthe surface A, the shape of the annulus or a ratio of the annulus isvariable by changing an interval between the optical elements 134 a and134 b, as shown in FIGS. 4B and 4C.

As described later, since the imaging optical system 140 is a zoomingoptical system, by changing the magnification and the aperture diameterof the stop 158, an effective light source having a desired size can beformed having a larger ratio of annulus, such as a 2/3 annulus and a 3/4annulus, than that formed by the light adjusting means 130.

When the conical optical element 134 is used, the restrictionrequirement of the incident angle of the light upon the fly-eye lens 156should be met. When the incident angle of the light exceeds a certainangle, the light becomes unnecessary light, deforms an effective lightsource and/or causes the uneven light intensity. It is thereforeeffective to maintain an interval between the optical elements 134 a and134 b and a magnification of the imaging optical system 140 within arestriction requirement of the incident angle of the fly-eye lens 156,and to vary the aperture diameter of the stop 158 so as to reduce theouter diameter and adjust the ratio of the annulus. This is not limitedto the annular illumination, but may apply the quadrupole and dipoleilluminations.

The conical surfaces of the optical elements 134 a and 134 b haveapproximately the same angle. The same angle restrains an angularincrease of the exit light from the light shaping means 122, andminimizes the light shielding by the subsequent optical system. When thesubsequent optical system has an angular leeway, the same angle is notnecessarily required and the angle may be varied for the reduced annularbreadth.

Instead of the conical optical element 134, other components may beused, such as a triangular roof type dipole converting element and aquadrupole converting element that can change an interval between anincident-side optical element that has a concave pyramid incidentsurface and an exit-side optical element that has a convex exit pyramidsurface. The shape formed by the light shaping means 120 may bemaintained without using the light adjusting means 130. Thus, acombination of the optical elements of the light shaping means 120 andthe light adjusting means 130 would be able to form a real image or avirtual image of the light having various shape distributions near thesurface A.

The zooming imaging optical system 140 changes a magnification of ashape formed on the surface A or the light turned into a desired shapeby the light adjusting means 130, and the resultant light is projectedonto an incident surface of the fly-eye lens 156 via the filter member154, which will be described later. The imaging optical system 140includes lenses 142, 144 and 146 in this embodiment, but the number oflenses is not limited.

When the light intensity distribution on the predetermined surface Aforms an image on the incident surface of the fly-eye lens 156 withoutaberration, the outline of the light intensity distribution ishighlighted and causes the uneven light intensity and the non-uniformityof the effective light source on the plate 400 that is a surface to beexposed. Therefore, an imaging relationship between the surface A andthe incident surface of the fly-eye lens 156 preferably containsaberrations (including the defocus) to some extent. This is not true asthe number of micro-lenses increases in the fly-eye lens 156 and theinfluence on the uneven light intensity is small.

In response to the incident light, the fly-eye lens 156 forms plurallight source images (or secondary light sources) near its exit surface,and uniformly illuminates the reticle 200 surface. A diameter variable(or switchable) stop 158 is arranged near the surface where plural lightsource images are formed, i.e., surface B. The surface where plurallight source images are formed (or the back focal surfaces of themicro-lenses in the fly-eye lens 156) has a relatively high energydensity of the light, and the stop 158 defocuses from this surfaceslightly (e.g. from minus several millimeters to plus severalmillimeters apart from this surface). Of course, if the stop 158 canendure the energy density, the stop 158 may be arranged on the surfacewhere plural light source images are formed.

The stop 158 and the aperture stop 310 are arranged in an approximatelyoptically conjugate relationship. At the exit surface side of the stop158, an image of the multiple light sources formed by the fly-eye lens156 and the stop 158 on the aperture stop 310 is the illumination lightshape (effective light source shape) at each point on the plate 400surface.

Among beams from plural light source images, the beams unrestricted bythe stop 158 effectively illuminate the surface on which the maskingblade 172 is arranged, via the condenser optical system 160. Due to theimaging optical system 180, the masking blade 172 is optically conjugatewith a surface where the reticle 200 is arranged, and determines anilluminated area on the reticle 200 surface. The condenser opticalsystem 160 of this embodiment includes lenses 162 and 164, and theimaging optical system 180 of this embodiment includes lenses 182 and184. However, the number of lenses of the optical systems 160 and 180 isnot limited.

The half-mirror 152 is provided between the lenses 162 and 164 in thecondenser optical system 160. The half-mirror 152 splits the incidentlight into the reflected light and the transmitting light, one of whichis used to illuminate the reticle 200, and the other of which is used toindirectly monitor the exposure dose incident upon the reticle 200 usinga detector 170. An arrangement between the half-mirror 152 and thedetector 170 is not limited to that shown in FIG. 1, and they may bearranged on the optical path from the light source section 102 to themasking blade 172. The detector 190 that measures the effective lightsource distribution is provided near the reticle 200, and can beinserted into and ejected from the optical path between the reticle 200and the projection optical system 300.

This embodiment arranges, as shown in FIG. 1, the deflection mirrors 150and 151 and the half-mirror 152 so that the optical path is arranged onone plane from the DOE shown in FIG. 2 to the plate 400 surface. As aresult, as described later, the filter member 154 has a simplestructure.

A description will be given of the filter member 154 and the σ shapecorrection mechanism 128.

Referring now to FIG. 1, a description will be given of thenon-uniformity of the transmittance distribution of the illuminationoptical system 110 caused by the mirrors 150 to 152. With respect to aprincipal ray a and rays b and c having predetermined NAs on a sectionparallel to the paper surface of FIG. 1, when there is no deflectionmirrors 150 and 151 and half-mirror 152, these rays are symmetrical withrespect to the optical axis, and have no difference in transmittance onthe optical path from the surface A to the reticle 200 surface. Even ifthese mirrors exist, no transmittance difference occurs with respect torays b and c if these rays b and c are parallel on each mirror.

However, due to the design restriction (or the space and aberrationoptimizations), it is difficult to strictly equalize the incident anglesupon the mirrors 150 and 151 and the half-mirror 152 in an actualconfiguration. Although no problems occur when these optical elementsare coated with a material whose transmittance or reflectance does notdepend upon the incident angle, the coating material is limited for thelight having a wavelength of 250 nm or smaller, e.g. the ArF excimerlaser with a wavelength of 193 nm, and the angular dependency of thecoating material becomes conspicuous. Therefore, the rays a to c havedifferent transmittances from the surface A to the reticle 200 surface.

FIG. 6 shows a graph showing one exemplary transmittance distribution.FIG. 7 shows exemplary two-dimensional transmittance distribution in thea distribution. The concentration in FIG. 7 indicates the non-uniformityof the transmittance distribution. Since incident angles of rays d and eupon each mirror located perpendicular to the paper surface on thesurface A are almost the same as the incident angle of the ray a, thetransmission distribution in the a distribution is approximatelyconstant in the X direction as shown in FIG. 7, but changes in the Ydirection. Therefore, even when the distribution that is symmetricalwith respect to the XY directions on the surface A, the a distributionon the reticle 200 surface has a weaker intensity in the Y directionthan that in the X direction. The exposure using this a distributionresult in different imaging performance to a pattern in the X directionand a pattern in the Y direction, causing the CD difference in twoorthogonal directions. In addition, when the projection optical system300 subsequent to the reticle 200 uses a mirror or is a catadioptricoptical system, the mirror makes the a distribution on the plate 400surface non-uniform, causing the imaging performance to a pattern in theX direction and a pattern in the Y direction, resulting in the CDdifference in two orthogonal directions, even if the a distribution onthe reticle 200 surface is uniform.

In other words, due to the non-uniform transmittance distribution to thepupil 310, the effective light source distribution becomes non-uniform.A first solution for this problem according to this embodiment arrangesthe first filter member 154 for making the transmission distributionuniform. In other words, the filter member 154 has a transmissiondistribution that cancels the non-uniformity of the transmissiondistribution caused by the mirrors in the illumination and projectionoptical systems.

This embodiment arranges the filter member 154 just before the fly-eyelens 156, but a position of the filter member 154 is not limited to thisposition, as long as it has substantially a Fourier transform with thereticle 200 surface that is the surface to be illuminated (or theposition conjugate with the pupil 310 surface). This embodiment attemptsto make uniform the transmission distribution up to the pupil 310, andthe pupil 310 has a Fourier transform relationship with the reticle 200and the exit surface of the fly-eye lens 156 is conjugate with the pupil310. The filter member 154 can be arranged near the incident or exitsurface of the fly-eye lens 156 or a surface that optically conjugatewith the incident or exit surface of the fly-eye lens 156. The reasonwhy the filter member 154 can be arranged at the incident surface of thefly-eye lens 156 is that the fly-eye lens 156 approximately maintainsthe effective light source between the incident and exit surfaces (orbefore and after the fragmentation) for each lens element. In thisrespect, the filter member 154 may be provided on the surface (orsurface A) which determines the base shape of the effective light sourceor on or near a position optically conjugate with the surface, and the“position that has substantially a Fourier transform relationship withthe surface to be illuminated” intends to cover the surface (or surfaceA) which determines the base shape of the effective light source or onor near a position optically conjugate with the surface.

FIGS. 8A and 8B show filter members 154 a and 154 b having differenttransmittance distributions. The filter member 154 a has a transmittancedistribution that is symmetrical with respect to the X-axis, and thefilter member 154 b has a transmittance distribution that slightlyoffsets the transmittance distribution of the filter member 154 a in theY direction. The concentrations in FIGS. 8A and 8B are transmittancedistributions that cancel out the reflectance and transmittancedifferences of the rays a to c on each mirror.

The filter member 154 can make the transmittance distribution on thepupil 310 approximately uniform or rotationally symmetrical. A designvalue of the illumination optical system 110 (that considers mirrors'reflectance and transmittance characteristics) may uniquely determinethis distribution. Alternatively, the detector 190 measures the adistribution on the reticle 200 surface, and the controller 500 mayselectively arrange one of the filter members 154. A large filter member154 may be arranged and shifted to the most suitable, calculatedposition in the Y direction for each apparatus and for each illuminationcondition.

Referring now to FIG. 9, a description will be given of a method fordetermining the transmittance distribution of the filter member 154.Here, FIG. 9 is a flowchart for setting the transmittance distributionof the filter member 154.

First, the illumination optical system 110 is designed to provide theuniform transmittance distribution on the pupil 310 without the mirrors150 to 152 (step 1002). It is preferable to arrange on a plane theoptical axis of the optical path from the light source section 102 tothe reticle 200 surface that is the surface to be illuminated, becausethe structure of the filter member 154 thereby becomes simple like afilter that varies a concentration in one direction.

Next, the non-uniformity of the transmittance distribution caused by theprojection optical system's mirror and the mirrors 150 to 152 in theillumination optical system is obtained through a simulation (step1004). The non-uniformity of the transmittance distribution can beobtained by comparing the transmittance distributions before and afterthe mirrors are inserted. If necessary, the non-uniformity of thetransmittance caused by other factors is obtained.

Next, the transmittance distribution is set to the filter member 154which corrects the non-uniformity of the transmittance distribution,which is caused by the mirrors in the projection and illuminationoptical systems, such as mirrors 150 to 152, and measured by step 1004(step 1006).

For example, when positions corresponding to rays a to e havetransmittances of 95%, 90%, 90%, 95% and 95% in the transmittancedistribution in FIG. 7, the transmittance distribution that cancels outthe non-uniformity of the above transmittance distribution, such as the90%, 95%, 95%, 90% and 90% at the above positions is set to the filtermember 154. Such a transmittance distribution applies to the filtermember 154 a.

On the other hands, for example, when positions corresponding to rays ato e have transmittances of 95%, 90%, 93%, 95% and 95% in thetransmittance distribution in FIG. 7, the transmittance distributionthat has the above transmittance distribution, such as the 90%, 95%,about 92%, 90% and 90% at the above positions a to e, as discussedabove, is produced, offset by a predetermined amount in the Y directionso as to provide the positions a to e with the uniformity of thetransmittance distribution, and set to the filter member 154. Such atransmittance distribution applies to the filter member 154 b. Whilethis example illustrates corrections at three points in the Y direction,it is preferable to measure or interpolate more fragmented points andset a filter member having a suitable distribution that cancels thenon-uniformity at these points.

The filter members 154 a and 154 b have substantially the samedistribution in the X direction, and different in a continuouslychanging distribution in the Y direction. This is because the mirrors150 to 152 are arranged so that the optical path is located on oneplane, as shown in FIG. 1, from the surface A that determines the baseshape of the effective light source and the reticle surface. Asdiscussed above, since the incident angles of the rays d and e upon eachmirror in a direction perpendicular to the paper surface areapproximately the same as those of the ray a, such a filter distributioncan correct the non-uniformity. Since the concentration of the filterchanges only in one direction, the manufacture of the filter is easy.For example, this filter is easily and inexpensively manufacturedthrough an evaporation using, for example, metal coating, by controllingpositions of two shielding plates between a substrate and an evaporationsource so as to form a unidirectional distribution on the substrate.

If the optical path from the surface A to the reticle 200 surface cannotbe located within one plane for configuration convenience of theillumination optical system 110, two filter members 154 that have each aunidirectional distribution may be arranged so that the distributiondirections are orthogonal to each other. Of course, two filter members154 may be arranged with their distribution directions orthogonal toeach other, even when the optical path from the surface A to the reticle200 surface is arranged on one plane. Each of these two filter membersor their transmission distributions may be independently shifted in thedistribution direction and positioned. If necessary, two or more filtermembers 154 may be provided. The two or more filter members 154 may havethe same transmittance distribution or different transmittancedistributions.

Next, the filter member 154 having the transmittance distribution set bystep 1006 is arranged on the optical path of the illumination opticalsystem 110 (step 1008). As discussed above, the arranged position is aposition that has substantially a Fourier transform relationship withthe surface to be illuminated. As a result, the transmittancedistribution of the filter member 154 corrects the non-uniformity of thetransmittance distribution caused by the mirrors in the illumination andprojection optical systems 110 and 300.

Whenever the illumination condition is changed, the controller 500 mayswitch the filter member 154. While a change of the illuminationcondition typically associates with a change of the a distribution onthe reticle 200 surface, the change of the illumination condition ofthis embodiment covers a change of the polarization while the adistribution is maintained. When the NA of the projection optical systemincreases as in the recent exposure apparatus, the imaging performancevaries due to the polarization of the light incident upon a wafersurface. So as to expose a finer pattern at a high NA or improve theimage quality, the polarization controlled illumination is effective.For example, the illumination light having a polarization direction inthe X direction is suitable for an L & S pattern that extends in the Xdirection. The exposure is thus optimized when the polarization isswitched in accordance with a pattern.

In general, the above mirrors have a polarization characteristicdifference in addition to the angular characteristic difference, asshown in FIG. 15. Therefore, the transmission distribution to theprojection lens's pupil 310 differs even when a distribution shape isthe same on the surface A if the polarization changes (in particular inthe above polarization controlled illumination). According to analternative embodiment, plural filter members 154 are provided on theswitching means, such as a turret, the detector 190 measures the adistribution on the reticle 200 surface, the controller 500 selects aproper filter member 154 from among the plural filter members 154whenever the illumination condition changes, and arranges the selectedone on the optical path.

In this case, the illumination optical system 110 may use a structureshown in FIG. 17. Here, FIG. 17 is an enlarged structure of theillumination optical system 110 shown in FIG. 1 for the polarizedillumination and for the non-polarized illumination. When the lightsource section 102 is a laser, the linearly polarized laser beam may beutilized. In addition, it is necessary to provide the illuminationoptical system 110 with the X-polarized light of a constant intensityirrespective of a difference of a polarization direction of the exitlaser beam caused by the laser's installation condition and thestructure of the laser deflection optical system. Thus, when thepolarization direction of the exit laser beam and the reflections by thedeflection mirrors 103, 104 and 112 provide the Y-polarized light, thepolarized light is preferably converted into the X-polarized light byutilizing a λ/2 phase plate 111.

A phase canceling (or adjusting) plate 113 is to convert the linearlypolarized light into randomly polarized light, inserted into the opticalpath during the non-polarized illumination and retreated from theoptical path during the polarized illumination. The mirrors 150 and 151are broadband high-reflection (“BBHR”) mirrors, and the BBHR coating isdesigned to restrain a phase difference that occurs on the coatingbetween the s-polarized light and the p-polarized light at broadbandincident angles.

154 denotes a ND filter, and 155 is a λ/2 phase plate. This embodimentprovides plural types of ND filters 154 and plural types of λ/2 phaseplates 155, and the ND filter 154 and the λ/2 phase plate 155 make apair. FIGS. 18A and 19A each show a pair of a different type of NDfilter 154 and λ/2 phase plate 155. FIG. 18A shows a schematic planeview of a pair of a ND filter 154 a and a λ/2 phase plate 155 a used forthe tangentially polarized illumination. FIG. 19A shows a schematicplane view of a pair of a ND filter 154 b and a λ/2 phase plate 155 bused for the cross-pole polarized illumination. The reference numeral154 generalizes 154 a and 154 b, and the reference numeral 155generalizes 155 a and 155 b.

The λ/2 phase plate 155 in the polarized illumination of this embodimentsets a predetermined polarization to each of plural areas in theeffective light source. The ND filter 154 is a filter membercorresponding to each area, and each filter member is preset to correctthe polarization difference among rays and the resultant non-uniformityof the transmittance distribution caused by the mirrors.

FIGS. 18B and 19B correspond to FIG. 6, and show the transmittancedistribution that depends upon the incident angles upon the ND filters154 a and 154 b. The ordinate of the graph denotes the transmittance.FIG. 18C shows one exemplary transmittance distribution set to the NDfilter 154 a. For example, the reason why the transmittance distributionhaving the transmittances of 90% and opening (100%) is set to the areasa and e of the ND filter 154 a in FIG. 18C, although the samepolarizations A and E are set as shown in FIG. 18A, is that the angulardependency of the transmittance shown in FIG. 18B is considered. Thereason why this embodiment sets the constant transmittance to one filteris that the modified illumination, such as a dipole illumination,usually used for the polarization controlled illumination uses a limitedarea, such as a dipole, and the transmittance difference that dependsupon the incident angle is small in the actually used area in thefilter. Thus, it is optional to consider the angular dependencycharacteristic in one filter.

In an attempt to use the phase plate 155 to generate differentpolarizations in different areas on the pupil 310, the filter member 154suitable for the polarization of each area is provided and corrects themirrors' influence that indicate different transmittances for each area.While FIG. 17 does not show that the controller 500 is connected to thefilter member 154 for illustration convenience, the controller 500 cancontrol the filter member 154 via a switching means (not shown). Thefilter member 154 and the phase plate 155 are exchanged in a pair. Thus,step 1008 is not limited to the initial arrangement of the filter member154.

The detector 190 uses, for example, two sensors, and can measure eachpolarization component, such as X-polarized light component andY-polarized light component. Of course, a position of the detector 190is not limited to this position. For example, the detector 190 may beprovided on the wafer stage. Alternatively, the detector 190 may belocated at a position of the light amount detector 170. However, thedetection at this point does not reflect the reflection and transmissioncharacteristics of the half-mirror 152 and the reflection characteristicof the mirror 151. Therefore, the effective light source distribution onthe surface to be illuminated needs to be calculated by consideringthese characteristics and redesigning the optical system.

The filter member 154 is not limited to an optical filter that changesan optical concentration distribution and may use, for example, amechanical light shielding part 155 that has different pitches and lightshielding widths in the Y direction, like a filter member 154 c shown inFIG. 8C. In FIG. 8C, black lines denote the light shielding parts 155,and white lines denote light transmitting parts. When a mechanical lightshield is located just before the fly-eye lens 156, the structureappears on the incident surface of the fly-eye lens 156 and affects thelight intensity distribution on the surface to be illuminated and adeviation of the a distribution at illuminated positions. Therefore, themechanical light shield is preferably separated from the incidentsurface of the fly-eye lens 156 by a predetermined amount to the extentthat the fine structure does not appear on the incident surface of thefly-eye lens 156.

The mechanical filter member 154 is particularly effective to acatoptric optical system that uses no refractive element as in anexposure apparatus that utilizes the extreme ultraviolet (“EUV”) as alight source. The structure of the EUV exposure apparatus is quitedifferent from the above exposure apparatus, and basically uses areflective optical system that includes only mirrors from the lightsource to the surface to be illuminated. Many mirrors may cause theasymmetry of the effective light source. One or plural mechanicalfilters like the filter member 154 near the pupil surface of the surfaceto be illuminated would be able to correct the non-uniformity.

While the above embodiment discusses the light shaping means 120 havinga DOE, this embodiment intends to correct the non-uniformity of the adistribution caused by the projection optical system's mirrors, theillumination optical system's mirrors 150 to 152, and other factors.Therefore, the DOE is not necessarily vital. As shown in FIG. 1, anyoptical system is apparently applicable to this embodiment as long asthe optical system forms a controlled, light shape distribution on thesurface A.

Alternatively, a separation from the ideal σ distribution is alsoeffective. For example, when a reticle pattern itself has a CDdirectional difference, when the projection lens' aberration causes adirectional difference of a pattern, and when an exposed CD differenceoccurs between a main scan direction and an orthogonal sub-scandirection in the exposure apparatus 1, a filter may be selected whichcorrects the directional difference of the actually exposed pattern.

A second solution for the problem of a non-uniform effective lightsource distribution due to the non-uniform transmittance distribution upto the pupil 310 is to change the effective light source and to make theintegral intensity uniform on the surface to be illuminated. Thisembodiment provides the σ shape correction mechanism 128 for thispurpose. The σ shape correction mechanism 128 may be used together withthe filter member 154 or they may be used singularly.

For a quick and easy adjustment, the preferred embodiment uses thefilter member 154 to correct the fixed a distribution transmittance thatdoes not depend upon the illumination condition, such as theillumination optical system's mirrors 150 to 152 and the projectionoptical system's mirrors, and uses the a shape correction mechanism 128for fine corrections for each illumination condition. The a shapecorrection mechanism 128 can bring the a distribution on the surface tobe illuminated close to the ideal one. In particular, the non-uniformityof the a distribution easily occurs due to the mirror, half-mirror andantireflection coating in the polarization controlled illumination. Thea shape correction mechanism 128 properly adjusts the non-uniformity inaccordance with a change of the polarization.

A separation from the ideal a distribution is also effective. Forexample, when a reticle pattern has a CD directional difference, whenthe projection lens' aberration causes a directional difference of apattern, and when an exposed CD difference occurs between the main scandirection and an orthogonal sub-scan direction in the exposure apparatus1, the symmetry of the a distribution is changed so as to correct the CDdirectional difference of the finally exposed pattern.

Referring now to FIG. 10, a description will be given of the operationof the a shape correction mechanism 128. Here, FIG. 10 is a view showingan operation of the a shape correction mechanism 128 when the lightshaping means 120 forms a uniform light intensity distribution on thesurface A, and the light intensity distribution on the surface A (as asectional view parallel to the paper surface). Each reference numeral inFIG. 10 corresponds to that in FIG. 1. The light emitted from the lightshaping means 120 forms a distribution having a predetermined shape onthe surface A. The light shaping means 120 that includes two or moreoptical integrators, such as a fly-eye lens, an internal surfacereflecting integrator, a DOE, etc. and a combination of thesecomponents, can provide a controlled distribution having a desired shapeon the surface A as well as a controlled distribution of the angularcharacteristic of the incident light. Of course, even when the lightfrom the light source fluctuates, the distribution and angularcharacteristics maintain constant. The σ shape correction mechanism 128includes light shielding members 129 a and 129 b.

In FIG. 10A, the light shielding members 129 a and 129 b of the σ shapecorrection mechanism 128 are located near the surface A, and set to suchstates that they do not restrict the light from the light shaping means120. Therefore, the light intensity distribution on the surface A ismaintained uniform.

FIG. 10B shows that the light shielding member 129 a is inserted intothe optical path in the state in FIG. 10A. Since the light shieldingmember 129 a shields the light, the distribution is partially lost onthe surface A. While the distribution on the surface A is then convertedinto another shape due to the light adjusting means 130, if necessary,the incident surface of the fly-eye lens 156 or the a distribution ispartially lost in accordance with the distribution shape on the surfaceA. Thus, the a distribution can be partially modified by varying thestate of the a shape correction mechanism 128. For example, themagnitude of the a distribution can be adjusted in two orthogonaldirections by inserting the light shielding member 129 b into theoptical path similar to the light shielding member 129 a. The controller500 moves the light shielding member 129 a, for example, based on anoutput of the detector 190. The controller 500 determines whether thedistribution of the effective light source shifts from a predetermineddistribution, and adjusts the effective light source via the a shapecorrection mechanism 128 based on the determination result. For example,when the transmittance is non-uniform, the controller 500 controls themovement of the light shielding member 129 a so as to provide a uniformintegral intensity of the effective light source distribution on thereticle 200 surface in plural directions from the optical axis.

FIG. 10C arranges the light shielding members 129 a and 129 b of the ashape correction mechanism 128 apart from the surface A. In this case,the distribution on the surface A is not partially lost unlike FIG. 10B,but maintains its outline and partially reduces its intensity. Thisconfiguration is preferable if it is necessary to maintain the outlineand partially reduce the intensity in the final a distribution. Thecontroller 500 controls a movement of the light shielding member 129 a,similar to FIG. 10B, based on an output from the detector 190. Thus, asimple structure can partially change the intensity by adjusting thelight shielding member in the σ shape correction mechanism 128. Theposition of the σ shape correction mechanism 128 from the surface A maybe adjusted if necessary or fixed in place. The position of the σ shapecorrection mechanism 128 is not limited to a position near the surface Abut may be a position near the incident surface of the fly-eye lens 156,for example.

FIGS. 11A to 11C are schematic plane views showing illustrativestructures of different types of a shape correction mechanisms 128. FIG.11A shows a σ shape correction mechanism 128 a that includes four,separately drivable, light shielding members 129. For example, thecontroller 500 obtains an output from the measuring part 190 shown inFIG. 1, and moves a position of each light shielding member 129 c basedon the output information so as to minimize the XY difference in theeffective light source shape. Alternatively, it may be possible to movea position of each light shielding member 129 c from the exposure resultso as to minimize a directional difference of an exposed pattern.

If the telecentricity, i.e., the perpendicularity of the light, on thereticle 200 surface changes as the σ shape correction mechanism 128 isdriven, one or more of lenses in the light shaping means 120 (or lens ofthe optical system 126) and one or more lenses in the zooming imagingoptical system 140 are decentered from the optical axis and adjusted. Ofcourse, the σ shape correction mechanism 128 may be driven to adjust thetelecentricity. The σ shape correction mechanism 128 can reduce thedecentering and non-uniformity of the σ distribution.

FIG. 11B shows a σ shape correction mechanism 128 b that includes eight,separately drivable, light shielding members 129 d. The σ shapecorrection mechanism 128 b provides multidirectional corrections. FIG.11C shows a σ shape correction mechanism 128 c that includes four lightshielding members 129 e having curved light shielding edges suitable forthe circular and annular shapes because the σ distribution usually usesthese shapes for the base shape.

Even in the polarized illumination, the σ shape correction mechanism 128may be used instead of or together with the filter member 154. In thiscase, the σ shape correction mechanism 128 b and a σ shape correctionmechanism 128 d shown in FIG. 16A are applicable to the filter member154 a and the phase plate 155 a shown in FIG. 18A. A σ shape correctionmechanism 128 e shown in FIG. 16B is applicable to the filter member 154b and the phase plate 155 b shown in FIG. 18B. The functions of the σshape correction mechanisms 128 d and 128 e are similar to those of theσ shape correction mechanisms 128 a to 128 c.

As the σ shape correction mechanisms 128 a to 128 e adjust the effectivelight source, the effective coherence factor σ reduces in a directionalong which the light shielding member moves to the center. In otherwords, the effective coherence factor σ decreases and reduces thedirectional difference. In this case, if the average magnitude of σreduces, the magnification of the zooming imaging optical system 140 ismade larger so as to adjust the average magnitude of σ.

The σ shape correction function may be used to aggressively modify theeffective light source, in addition to the fine correction of its shape.For example, this function provides a dipole illumination state from theannular illumination and the quadrupole illumination.

The reticle 200 is made, for example, of quartz, has a circuit pattern(or an image) to be transferred, and is supported and driven by areticle stage (not shown). The diffracted light through the reticle 200is projected through the projection optical system 300 onto the plate400. The reticle 200 and the plate 400 have an optically conjugaterelationship. Since the exposure apparatus 1 of this embodiment is astep-and-scan type exposure apparatus (also referred to as a “scanner”),it scans the reticle 200 and the plate 400 at a speed ratiocorresponding to a reduction ratio, and transfers the pattern of thereticle 200 onto the plate 400. When the exposure apparatus 1 is astep-and-repeat type exposure apparatus (also referred to as “astepper”), the reticle 200 and the plate 400 are kept stationary duringexposure.

The projection optical system 300 is an optical system that projects apattern of the reticle 200 onto the plate 400. The projection opticalsystem 300 has an aperture stop on the pupil 310 that arbitrarily setsan NA. The aperture stop makes variable the aperture diameter thatdefines the NA of the imaging light on the plate 400 and varies theaperture diameter to obtain the necessary NA. In this embodiment, thecoherence factor σ is a ratio between the size of the images of theplural light sources formed by the fly-eye lens 156 at the position ofthe aperture stop and the aperture diameter of the aperture stop.

The surface B that forms multiple light sources and the diametervariable aperture stop in the projection optical system are arranged atapproximately optically conjugate positions, and the distribution on thesurface B is substantially the σ distribution or effective light sourceon the plate 400 surface. When the stop 158 is installed on the surfaceB, the distribution that is not shielded by the stop 158 forms the σdistribution. When no stop 158 is provided on the surface B and thefly-eye lens 156 has sufficiently fine rod lenses (e.g. several tens ofrows in one direction), the distribution on the incident surface of thefly-eye lens 156, which is formed by a combination of the light shapingmeans 120, light adjusting means 130 and the imaging optical system 140,determines the effective σ distribution.

A position of the stop 158 is not limited to a position near the surfaceB. For example, the stop 158 may be inserted b into an optical path onthe surface A by the switching means, such as a turret, together withthe light adjusting means 130 or may be arranged just before the fly-eyelens 156 or arranged at these plural positions simultaneously. Forexample, a desired σ distribution can be formed by arranging at aposition of the beam changing means 130 a stop having a mechanism thatdoes not restrict a radial direction that is a direction for restrictingthe size and can vary only an aperture angle, such as a quadrupole, byarranging an iris stop that restricts the size just before the fly-eyelens 156, and by arranging a fixed stop on the surface B. A versatile σcondition can be produced by arranging stops having different functionsat plural positions and by changing and switching these stops.

While the projection optical system 300 of this embodiment is an opticalsystem that includes plural lens elements 320 and 322, it may use acatadioptric optical system comprised of a plurality of lens elementsand at least one mirror, an optical system comprised of a plurality oflens elements and at least one DOE such as a kinoform, and a catoptricoptical system, and so on. Any necessary correction of the chromaticaberration may use a plurality of lens units made from glass materialshaving different dispersion values (Abbe values), or arrange a DOE suchthat it disperses in a direction opposite to that of the lens unit. Insuch a catadioptric optical system, even when the non-uniformity of thetransmittance distribution in the illumination optical system 110 iscorrected, the non-uniformity of the transmittance distribution occurson the projection lens's pupil 310 due to the mirror in the projectionoptical system. It is therefore necessary to arrange the filter and stopthat cancel the non-uniformity of the transmittance distributiongenerated by mirrors in both the illumination and projection opticalsystems. An alternative embodiment fills the space between the finalsurface of the projection optical system 300 and the plate 400 with aliquid, such as pure water. An effect of the polarization control isparticularly remarkable in such an immersion type projection exposureapparatus due to the high NA scheme.

The plate 400 is a wafer in this embodiment, but it may include a liquidcrystal plate and a wide range of other objects to be exposed.Photoresist is applied onto the plate 400.

The plate stage 450 supports the plate 400. The plate stage 450 may useany structure known in the art, and a detailed description of itsstructure and operations will be omitted. For example, the plate stage450 uses a linear motor to move the plate 400 in a direction orthogonalto the optical axis. The reticle 200 and plate 400 are, for example,scanned synchronously, and positions of the reticle stage (not shown)and plate stage 450 are monitored, for example, by a laserinterferometer and the like so that both are driven at a constant speedratio. The plate stage 450 is installed on a stage stool supported onthe floor and the like, for example, via a damper. The reticle stage(not shown) and the projection optical system 300 are a barrel stool(not shown) that is supported on a base frame placed on the floor, forexample, via a damper.

In exposure, the light emitted from the light source section 102Koehler-illuminates the reticle 200 via the illumination optical system110. The light that passes the reticle 200 and reflects the reticlepattern forms an image on the plate 400 via the projection opticalsystem 300. The exposure apparatus 1 forms a desired effective lightsource using the filter member 154 and/or the σ shape correctionmechanism 128, and provides high-quality devices (such as semiconductordevices, LCD devices, image pick-up devices (such as CCDs), thin filmmagnetic heads, and the like).

While the above embodiments simply describe use of both the filtermember 154 and the σ shape correction mechanism 128, the followingdescription discusses a more concrete embodiment.

A description will now be given of a selection of the filter member 154.As discussed above, it is preferable to install the filter member 154that corrects the fixed asymmetry that does not depend upon theeffective light source distribution or the asymmetry caused by themirrors. The transmittance distribution of the installed filter 154 isdetermined by one of the following methods:

A first method uses design values of the mirrors between the surface Aand the surface to be illuminated and a measurement result of thereflection or transmission characteristics of the manufactured mirrors,calculates the transmittance distribution in the σ distribution, andselects the filter member having a distribution that cancels out thenon-uniform distribution.

A second method irradiates a distribution that has an effective σ areathat is made as uniform as possible on the surface A, onto the incidentsurface of the fly-eye lens, and measures the actual effective lightsource distribution on the surface to be illuminated. Then, this methodcompares an effective light source distribution incident upon thesurface A, which is predicted on the surface to be illuminated withoutany mirror, or a designed effective light source distribution, with anactual effective light source distribution. Finally, this method selectsa filter having such a distribution that the actual effective lightsource distribution is approximately the same as the designed effectivelight source distribution.

A third method actually exposes a pattern in two directions, such as theXY directions, using a typical illumination mode, such as an annularillumination in which the outer side has a larger σ, and selects afilter member that equalizes the size of a pattern in the X direction tothe size of a pattern in the Y directions.

The determination methods thus select the filter member 154. Forexample, the illumination optical system that controls the polarizationmay select the filter member for each polarization. In the illuminationoptical system that controls the polarization, the polarization isclassified into five groups as shown in FIGS. 14A to 14E. Here, FIGS.14A to 14E show the polarizations of the lights in the σ distribution.More specifically, FIG. 14A shows a normal illumination that uses thenon-polarized light or the circular illumination. FIG. 14B shows anillumination that utilizes a linearly polarized light in the Ydirection. FIG. 14C shows an illumination that utilizes a linearlypolarized light in the X direction. FIG. 14D shows a tangentiallypolarized illumination. FIG. 14E shows a radially polarizedillumination.

One filter is prepared for each polarization, and these filters arearranged on a turret and switched according to the polarization to beset. Of course, irrespective of the polarization, only one filter thatis optimized, for example, to the non-polarization may be installed.

It is conceivable to use plural phase plates and to generate differentpolarizations in different areas on a pupil as shown in FIGS. 16A and16B. In this case, the transmittance can be different for each area dueto the influences of the mirrors, but it is preferable to provide eacharea with a filter suitable for the polarization of each area and tocorrect the transmittance distribution on the entire pupil. Since thetransmittance distribution varies as the polarization varies, it ispreferable to replace or combine a filter with one suitable for eachpolarization as the phase plate switches. For example, suppose thatseveral types of polarizations for use with the exposure are known, andseveral types of phase plates that form polarizations are prepared on aturret. By previously obtaining a filter suitable for the polarizationgenerated with each phase plate, and by installing the filter on theturret that moves in synchronization with the phase plate turret, thefilter suitable for the polarization is preferably varied as the phaseplate turret is moved and the polarization is varied.

A description will now be given of the setting of the σ shape correctionmechanism 128. The σ shape correction mechanism 128 is set at a positionin accordance with a change of the illumination condition. One of thefollowing setting methods is applicable:

A first method measures the effective light source distribution usingthe detector 190, etc. while the σ shape correction mechanism 128 doesnot restrict the light. The measured effective light source distributionis divided into plural areas, e.g., four areas, and the light intensityratio among these areas is measured. The light shielding members in theσ shape correction mechanism 128 are driven so that the light intensityratio becomes a desired value.

A second method exposes plural patterns that extend plural directions,e.g., two directions, while the σ shape correction mechanism 128 doesnot restrict the light. The light shielding members in the σ shapecorrection mechanism 128 are driven so that the CD difference amongthese patterns becomes a desired difference.

While the simultaneous use of these two means is discussed above, evenuse of only a single means is significantly effective.

In the illumination optical system that controls the polarization, thelight shielding members may be driven for each polarization. In theillumination optical system that controls the polarization, thepolarizations are as shown in FIGS. 14A to 14E, and the light shieldingmembers may be driven for each polarization. Of course, the lightshielding members may be driven always to a position optimized, e.g., anon-polarization, irrespective of the polarization.

In addition, it is conceivable to generate a different polarization fora different area on the pupil using plural phase plates, as shown inFIG. 16. In this case, the transmittance differs among areas due to theinfluence of the mirrors, etc., but the intensity distribution may becorrected without correcting the outline of the effective light sourceor changing the outline, by driving the light shielding member to aposition suitable for the polarization for each area. Since thetransmittance distribution varies whenever the polarization varies, astop is preferably turned to one suitable for each polarization as thepolarization or the phase plate varies.

For example, suppose that several types of polarizations for exposureare known, and several types of phase plates for forming thepolarizations are prepared in advance using a turret, etc. Preferably,an optimal stop shape and structure (including a width and position ofeach light shielding plate and the number of light shielding plates) arestudied to the polarization generated with each phase plate, andarranged on the turret that moves in synchronization with the phaseplate's turret so that the stop optimal to the polarization switches asthe phase plate's turret moves and the polarization varies. In addition,whenever the polarization varies minutely, the light shield member ispreferably driven.

Referring now to FIGS. 12 and 13, a description will now be given of anembodiment of a device manufacturing method using the above exposureapparatus 1. FIG. 12 is a flowchart for explaining a fabrication ofdevices (i.e., semiconductor chips such as IC and LSI, LCDs, CCDs,etc.). Here, a description will be given of a fabrication of asemiconductor chip as an example. Step 1 (circuit design) designs asemiconductor device circuit. Step 2 (reticle fabrication) forms areticle having a designed circuit pattern. Step 3 (wafer preparation)manufactures a wafer using materials such as silicon. Step 4 (waferprocess), which is referred to as a pretreatment, forms actual circuitryon the wafer through photolithography using the mask and wafer. Step 5(assembly), which is also referred to as a post-treatment, forms into asemiconductor chip the wafer formed in Step 4 and includes an assemblystep (e.g., dicing, bonding), a packaging step (chip sealing), and thelike. Step 6 (inspection) performs various tests for the semiconductordevice made in Step 5, such as a validity test and a durability test.Through these steps, a semiconductor device is finished and shipped(Step 7).

FIG. 13 is a detailed flowchart of the wafer process in step 4. Step 11(oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms aninsulating film on the wafer's surface. Step 13 (electrode formation)forms electrodes on the wafer by vapor disposition and the like. Step 14(ion implantation) implants ions into the wafer. Step 15 (resistprocess) applies a photosensitive material onto the wafer. Step 16(exposure) uses the exposure apparatus 1 to expose a reticle patternonto the wafer. Step 17 (development) develops the exposed wafer 47.Step 18 (etching) etches parts other than a developed resist image. Step19 (resist stripping) removes disused resist after etching. These stepsare repeated, and multilayer circuit patterns are formed on the wafer.This device manufacturing method can manufacture higher-quality devicesthan the conventional method. Thus, the device manufacturing method thatuses the exposure apparatus 1, and its resultant (intermediate andfinal) products also constitute one aspect of the present invention.

Further, the present invention is not limited to these preferredembodiments, and various variations and modifications may be madewithout departing from the scope of the present invention.

The exposure apparatus 1 of this embodiment arranges mirrors in such away that the optical path is arranged on one plane from the surface Athat forms a base shape of the effective light source to the reticle 200surface. In addition, the exposure apparatus 1 arranges the filtermember 154 that corrects the mirror characteristic, near the effectivelight source forming surface, so as to facilitate a formation of theoptical configuration, to make the σ distribution symmetrical withrespect to the optical axis, and to reduce the HV difference of anexposed pattern, which is caused by the effective light source.Moreover, the exposure apparatus 1 arranges the σ shape correctionmechanism 128 that has plural, separately drivable, light shieldingmembers near the surface A, so as to make the σ shape variable, andreduce the HV difference of the exposed pattern which does not attributeto the illumination optical system. Furthermore, the exposure apparatus1 arranges, at plural positions, light shielding members for defining anillumination condition (such as a fixed stop, a variable stop, an irisstop, and a σ shape correction mechanism), divides the functionality,and provides more diversified illumination conditions.

This application claims a benefit of foreign priority based on JapanesePatent Applications Nos. 2004-166552, filed on Jun. 4, 2004 and2005-116585, filed on Apr. 14, 2005, each of which is herebyincorporated by reference herein in its entirety as if fully set forthherein.

1. An illumination optical system illuminating a surface to beilluminated using light from a light source, comprising: a light shapingmember for transforming the light from the light source and for forminga predetermined light shape on a Fourier transform surface that has aFourier transform relationship with the surface to be illuminated; aneffective light source forming member for forming an effective lightsource using a light from the light shaping member as an incident light;and a plurality of light shielding members that are arranged near theFourier transform surface and that shield a part of the lighttransformed by the light shaping member and that are movableindependently from each other; wherein the plurality of the lightshielding members move based on the change of a shape of the effectivelight source.
 2. The illumination optical system according to claim 1,wherein the plurality of the light shielding members are movable in adirection orthogonal to an optical axis of the illumination opticalsystem.
 3. An illumination optical system illuminating a surface to beilluminated using light from a light source, comprising: a light shapingmember for transforming the light from the light source and for forminga predetermined light shape on a Fourier transform surface that has aFourier transform relationship with the surface to be illuminated; aneffective light source forming member for forming an effective lightsource using a light from the light shaping member as an incident light;a plurality of light shielding members that are arranged near theFourier transform surface and that shield a part of the lighttransformed by the light shaping member and that are movableindependently from each other; and a polarization setting member forsetting a polarization of the effective light source, wherein theplurality of the light shielding members move based on the change of atleast one of a shape of the effective light source and the polarizationof the effective light source.
 4. An illumination optical systemilluminating a surface to be illuminated using light from a lightsource, comprising: a light shaping member for transforming the lightfrom the light source and for forming a predetermined light shape on aFourier transform surface that has a Fourier transform relationship withthe surface to be illuminated; an effective light source forming memberfor forming an effective light source using a light from the lightshaping member as an incident light; and a plurality of light shieldingmembers that are arranged near the Fourier transform surface and thatshield a part of the light from the light source; wherein each of theplurality of the light shielding members is insertable into andejectable from the optical path at each of a plurality of positions inan optical axis direction of the illumination optical system.
 5. Theillumination optical system according to claim 4, the plurality of thelight shielding members comprising: a first light shielding member thatis insertable into and ejectable from the optical path near a firstplane that has a Fourier transform relationship with the surface to beilluminated; and a second light shielding member that is insertable intoand ejectable from the optical path near a second plane that has theFourier transform relationship with the surface to be illuminated. 6.The illumination optical system according to claim 5, wherein theplurality of the light shielding members include a plurality of thefirst light shielding members, and the plurality of the first lightshielding members are switched to be arranged in the optical path of theillumination optical system.
 7. The illumination optical systemaccording to claim 6, wherein the plurality of the light shieldingmembers include a plurality of the second light shielding members, andthe plurality of the second light shielding members are switched to bearranged in the optical path of the illumination optical system.
 8. Theillumination optical system according to claim 4, wherein at least oneof the plurality of the light shielding members is an iris stop.
 9. Theillumination optical system according to claim 4, wherein an apertureangle of the effective light source is determined by one of theplurality of the light shielding members.
 10. The illumination opticalsystem according to claim 4, further comprising a polarization settingmember for setting a polarization of the effective light source.
 11. Anillumination optical system illuminating a surface to be illuminatedusing light from a light source, comprising: a light shaping member fortransforming the light from the light source and for forming apredetermined light shape on a Fourier transform surface that has aFourier transform relationship with the surface to be illuminated; aneffective light source forming member for forming an effective lightsource using a light from the light shaping member as an incident light;a first light shielding member that shields a part of the light from thelight source and that is insertable into and ejectable from the opticalpath near the Fourier transform surface; and a second light shieldingmember that are arranged near the Fourier transform surface and thatshield a part of the light from the light source, the second lightshielding member including a plurality of light shielding portions thatare movable independently from each other.
 12. The illumination opticalsystem according to claim 11, wherein the first light shielding memberis an iris stop.
 13. The illumination optical system according to claim11, wherein an aperture angle of the effective light source isdetermined by the first light shielding member.
 14. The illuminationoptical system according to claim 11, further comprising a polarizationsetting member for setting a polarization of the effective light source.15. An illumination optical system illuminating a surface to beilluminated using light from a light source, comprising: a light shapingmember for transforming the light from the light source and for forminga predetermined light shape on a Fourier transform surface that has aFourier transform relationship with the surface to be illuminated; aneffective light source forming member for forming an effective lightsource using a light from the light shaping member as an incident light;a plurality of light shielding members that are arranged near theFourier transform surface and that shield a part of the light from thelight source; wherein each of the plurality of the light shieldingmembers includes a plurality of light shielding portions that aremovable independently from each other.
 16. The illumination opticalsystem according to claim 15, further comprising a polarization settingmember for setting a polarization of the effective light source.